Herald & Vitesse Forum

Rear Differential leakage

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caddis Chip Addis
Wayne, PA, USA   USA
I have a 1967 Herald 1200. I have been getting some leakage from the differential. As has been suggested on this forum, I cleaned the area around the vent and made sure the cotter pin was loose and free of gunk and that has not stopped the leakage. First question is how do I stop the leak? Although not a huge leak, just annoying as I have a pizza box under there soaking up the gear fluid all the time. Second question is how much gear fluid should go in the diff? There is a drain/bolt on the side of the diff and I am able to use a dropper to add gear oil. Should I add until the point that the oil starts coming out of the drain? Any suggestions are welcome!
Chip Addis

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VitesseEFI Nick Jones
Yeovil, Somerset, UK   GBR

The diff holds about a pint (so not much to lose) and is topped up using the filler plug halfway up the side of the rear housing. Just fill until it starts overflowing.

Where's it leaking from? Favourite spot is the input shaft seal which can drip all the time (it's below the correct oil level) but especially when driving. The cure for this is to drop the propshaft (driveshaft in US), remove the split pin and undo the centre nut. You can then pull / tap the flange off (be ready to catch the oil!) dig out the old oil seal and fit a new one. The original ones are leather, you can still get those or use a modern rubber one. Mark sure the surface the seal runs on is not grooved or rusted. If so it can be reclaimed with a "speedi-sleeve" or similar.

They can also leak from the side shafts though only when running as they are above the static oil level. Changing these is more work as you have to remove the half shafts, then extract the quarter shafts from the diff, then pull the bearings off after removing the spring clips. This can be difficult as they are tight and you should plan to replace the bearings too as they can be damaged during removal. Once the bearings are off the seal plate comes right off and the seals are easy to swap.

If leaking from the joint between front and rear casing it probably means it's been apart before and not properly reassembled. On solution is to remove it, split the casing and sort the problem.

Only other possibility (and fairly long shot) is that one of the spring mounting studs is missing and oil is being sprayed up through the hole when the car is moving. Seen it once on a Mk3 Spit that had had a swing spring fitted but not had the two extra stud holes blocked.

Hope this helps


caddis Chip Addis
Wayne, PA, USA   USA
Thanks, Nick! Great explanation and huge help to me. I'll have to do some investigative work to determine origin of leak(s). Fortunately, it's not really bad just more annoying as I need to keep a pizza box under that area to catch the drips.
Best regards,
Chip Addis

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